The present invention relates to methods and systems for dehumidifying air for use in dryers and air conditioners.
For a variety of reasons, it is desirable to reduce the moisture content of the air. For example, in certain industrial operations (e.g., the manufacture of integrated circuits), it is desirable to maintain the air within the manufacturing facility at a low relative humidity. Additionally, in warehouses which store material subject to corrosion, it has been found that a lower relative humidity within the warehouse inhibits the corrosion of the materials. Other applications that require air with a lower relative humidity include drying products (e.g., farm products such as grain) and the air supplied to the inlet of gas turbine engines. Furthermore, the energy costs related to air conditioning can be minimized through the use of a dehumidifier.
Methods for removing water vapor in gases may generally be classified into four methods: compression method, an adsorption/absorption method, a cooling method, and a membrane separation method. Efficiency, space limitations, and the application to which the dehumidified air will be applied are all considerations that might be addressed when choosing a method for dehumidifying air.
The absorption method of dehumidification may include the use of a desiccant solution that absorbs water vapor in the air. A number of liquids are commonly used as desiccants such as lithium bromide, lithium chloride, ethylene glycols, and potassium formate. When practicing an absorption method of dehumidification, a desiccant is sprayed into an air stream at a spray chamber. As the air stream flows through the spray of desiccant, water vapor in the air stream is absorbed into the desiccant causing the air to be dehumidified. As the desiccant absorbs water, it becomes diluted. To maintain the dehumidifying capacity of the system, the absorbed water must be removed from the desiccant. This is typically accomplished at a boiler where water is evaporated from the desiccant. After water has been evaporated from the desiccant, the concentrated desiccant from the boiler is cycled back to the spray chamber where the desiccant again absorbs water from the air stream.
One aspect of the present invention relates to a system for dehumidifying air. The dehumidifying system includes a multiple effect evaporator that efficiently creates a concentrated desiccant solution. The desiccant solution from the multiple effect evaporator is transferred to a desiccant spray chamber that sprays the desiccant solution into an air stream. The desiccant solution absorbs water vapor from the air stream. A conduit transfers at least some of the desiccant containing the absorbed water back to the multiple effect evaporator for removal of the water from the desiccant solution. Thereafter, the concentrated desiccant is cycled back to the spray chamber, and the process is repeated. In embodiments where it is desirable to cool the air stream, a cooling structure can be used to cool the desiccant before the desiccant is sprayed into the spray chamber. To further cool the air stream, an air cooler can be positioned downstream from the spray chamber.
The present invention also relates to a method for dehumidifying air. The method includes providing a water and desiccant solution to a multiple effect evaporator for producing a concentrated desiccant solution. The concentrated desiccant solution is transferred to a spray chamber where the desiccant solution is sprayed into an airflow stream. The sprayed desiccant absorbs water vapor from the air creating a water and desiccant solution that is transferred to the multiple effect evaporator for removal of water from the desiccant solution. If air conditioning is desired, dehumidified air exiting the desiccant spray chamber can be cooled by a method of cooling air. In such embodiments, a cooling structure can also be used to cool the desiccant before the desiccant is sprayed into the spray chamber.